Linear peristaltic pump with reshaping fingers intedigitated with pumping elements

ABSTRACT

A linear peristaltic pump of the type for removable engagement of a portion of a flexible tubing and having a plurality of sequentially actuated pumping elements which act along the engaged portion of the flexible tubing, with the pumping elements reciprocated in a first direction to collapse adjacent segments of the tubing and then in a second direction to release the adjacent segments of the tubing, each pumping element reciprocated in a sequence so that fluid in the flexible tubing is moved along the engaged portion of the tubing. The linear peristaltic pump further comprises a plurality of opposed pairs of pivotable reshaping fingers, with each pair of the reshaping fingers interposed adjacent to one of the pumping elements in sequence along the engaged portion of the flexible tubing. A finger drive and follower mechanism is formed by and engaged between each of the plurality of pairs of reshaping fingers and the adjacent ones of the pumping elements for actuating the reshaping fingers into reshaping engagement with the flexible tubing upon release thereof by the adjacent one of the pumping elements.

This application is a continuation of application Ser. No. 08/349,906filed Dec. 06, 1994 now U.S. Pat. No. 5,660,529.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a linear peristaltic pump for providingadjustable volumetric flow through a flexible fluid-filled tubing, suchas with infusion, of intravenous solutions through a flexible IV tubing.Particularly, the invention relates to a pump having plurality ofpumping elements or plungers which operate sequentially and repeatedlyalong a portion of the flexible fluid carrying tubing to squeeze thefluid therealong with a "milking" type of action. Fluid is forcedthrough the tubing from the entry end to the output end in the directionof the sequential actuation of the pumping elements. The volumetric flowrate is adjusted by changing the rate of sequential and repeatedsqueezing.

BACKGROUND OF THE INVENTION

Traditionally intravenous infusion has been accomplished using gravityflow systems or drip regulated systems. Modern advances for regulatingintravenous infusion have included various types of volumetric pumpingsystems. In situations where a patient is already established with agravity-fed or drip-type IV, it often becomes helpful to convert thesame system into one with a pump-controlled volumetric flow. Forexample, an emergency IV can be established in the field by paramedics,and upon arrival at a hospital, a doctor may need to administermedication at a precisely controlled flow rate. The same IV tubingsystem can then be conveniently adapted for controlled volumetric flowpumping through the use of various types of peristaltic pumps whichengage the exterior of the established IV tubing. The typical IV tubingis made of a medical grade polyvinyl chloride (PVC) which has thin wallsand is both flexible and resilient. Other more expensive tubing has beenproposed to reduce collapsing, but at a cost of about ten times as muchas PVC tubing. Alternatively, a combination of types of tubing has beenproposed, such as silicon tubing spliced along a length which will besubjected to peristaltic pumping action. Such combination systems canalso have a cost significantly greater than PVC (about five to eighttimes as much), because of the materials, splicing and additionalsterilization required. Pumps which act upon the outside of the tubingwalls to pump fluid within the tubing at a controlled rate permit themedical practitioners to avoid disturbing existing catheters or needlesalready established into the patient.

Thus, various types of modern pumps have been used for pumping fluidthrough an IV tubing, including pumps with a rotating arm, with rollersaffixed at both ends of the arm. The rollers are positioned adjacent acurved IV holding channel to engage and roll along a section of tubingplaced into the holding channel, thereby advancing a column of liquidtherethrough. As the arm rotates, the rollers alternately engage thetubing, one behind the other, and successive columns of liquid are movedthrough the tubing. Rotation of the arm continues and repeats thepumping action.

Another type of pump is one which is referred to as a single-plungerperistaltic pump. This type of pump has an entry valve which compressesthe tubing shut at an upstream point. A single elongated plunger thensqueezes a predetermined length of the tubing along a linear sectionahead of the closed entry valve. An outlet valve then compresses thetubing downstream from the elongated plunger after the liquid in thelinear section is squeezed out and moved toward the patient. With theoutlet valve closed, the entry valve is opened and the elongated plungeris retracted to allow fluid to move back into the linear section betweenthe entry valve and the outlet valve. The entry valve is then closed,and the outlet valve is opened so that compression of the singleelongated plunger can pump more fluid through the tubing.

Another type of pump, which is referred to here as a linear peristalticpump, uses a series of pumping elements which each engage andsequentially compress a plurality of small segments along an engagedportion of the IV tubing. Each pumping element in sequence at itsmaximum stroke acts as a seal valve to prevent unwanted reverse flow.Separate inlet and outlet valves are not required in such a linearperistaltic pump. The sequence repeats, and the pumping elementreciprocating strokes are typically timed to repeat the milking cyclewithout interruption. The rate of flow is controlled by changing therate of reciprocation while the magnitude of the stroke is constant.

With each of the various types of peristaltic pumps described above, theIV tubing is repeatedly collapsed to force the fluid out of the tubingin one direction and then released to allow fluid to reenter from theother direction. After a period of use, the PVC tubing material becomesprogressively flattened and permanently deformed such that the wallsbecome creased and the interior volume of the tubing changes over thenormal time period of operation. Tubing subject to permanent deformationreduces the pumping efficiency and reduces the accuracy of the pump. Tothe extent that attempts at reshaping may cause additional crease lines,the risk of premature cracking, tearing or rupture may also beincreased, particularly at crease lines. Thus, the tubing must bechanged frequently and must be carefully monitored to avoid lostefficiency, inadequate flow, inaccurate and improper volumetric flow orother failure of the system.

SUMMARY OF THE INVENTION

The present invention provides advantages of a linear peristaltic pumpand overcomes many of the difficulties which arrive with other types ofperistaltic pumps. The use of a linear peristaltic pump with a pluralityof sequentially actuated elements does not require separate entry andoutlet valves as with the single plunger type of peristaltic pump. Thepresent invention further provides reshaping fingers, which engage aflexible fluid-filled tubing, such as an IV tubing, adjacent to eachpumping element contact point, thereby continuously returning the tubingto a constant internal volume and thus maintaining a constant flow rateduring operation at a given speed. The time of operation before thetubing becomes permanently deformed is increased. A plurality of pairsof interdigitated reshaping fingers are used and are sequentiallyactuated transverse to the actuation direction of the pumping elementsalong the engaged length of the tubing. The interdigitated positioningof the reshaping fingers with the pumping elements advantageouslyfacilitates reshaping of the tubing immediately adjacent each of thecompression elements so that reshaping of the tubing is effectivelyaccomplished. Further, the present invention provides pairs of opposedreshaping fingers, each having concave jaws which the shape of acylindrical arc matching the outside diameter of the flexible tubing.The unique arc shape of the jaws, and particularly a substantial arc ofmore than about 90°, is made possible by the interdigitation of thefingers with the pumping elements so that reshaping does not interferewith the pumping elements. The result is to round the tubing to itsoriginal dimensions without adding additional stress or fatigue andwithout causing additional potential rupture corners.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects, advantages, and features, as well as otherobjects and advantages, will become more apparent with reference to thedescription and drawings below, in which like numerals represent likeelements and in which:

FIG. 1 is a schematic perspective view of one example of an operationalcontrol box for a linear peristaltic pump, depicting an example of theinventive pumping and reshaping mechanism, shown mounted in the controlbox at a position for engagement with an IV tubing according to thepresent invention;

FIG. 2 is a schematic perspective, partial cutaway view of an example ofthe inventive pumping and reshaping mechanism, including a plurality ofpumping elements, which, in this embodiment, are in the form of pumpingelement plates and with interdigitated reshaping fingers andvariable-speed drive motor according to the present invention;

FIG. 3 is a top schematic plan view of a portion of the pumping andreshaping mechanism of FIG. 2 showing a plurality of pumping elementplates and interdigitated reshaping fingers according to the presentinvention;

FIG. 4 is a schematic perspective view of a plurality of pumping elementplates and a plurality of interdigitated reshaping fingers as in FIG. 3;

FIG. 5 is a partial schematic cross-sectional view taken along sectionlines 5--5 of FIG. 3 showing a plurality of sequentially actuatedelements and reshaping fingers in which middle ones of the pumpingelements are shown actuated to compress a flexible tubing and in whichend ones of the interdigitated reshaping fingers are shown actuated toreshape the flexible tubing at points adjacent to retracted end pumpingelements;

FIG. 6 is a schematic end view showing one pumping element plate in aretracted position so that the flexible tubing is opened at that pointand showing the position of an adjacent pair of reshaping fingers(partially shown with hidden lines) engaged with the flexible tubingwhen it is released by the pumping element to reshape it to a circularcross-section, corresponding to an opened position in a pumpingsequence;

FIG. 7 is a schematic end view of the pumping element plate and adjacentpair of reshaping fingers of FIG. 6 shown in a subsequent partiallycompressed position in the pumping sequence;

FIG. 8 is an end view of the pumping element plate and adjacent pair ofreshaping fingers of FIGS. 6 and 7, shown with the pumping element in afully compressed position during the pumping sequence so that the tubingis closed and the adjacent pair of reshaping fingers are completelyretracted from the tubing according to one embodiment of the presentinvention;

FIG. 9 is an end view of the pumping element plate and reshaping fingersof FIGS. 6, 7 and 8 shown with the pumping element in a partiallyretracted position and with the reshaping fingers shown partiallyactuated to engage with the tubing for reshaping;

FIG. 10 is an end view of an alternative embodiment of a pumping elementplate and reshaping fingers shown in a position in which said pumpingelement is retracted and said reshaping fingers are fully actuated intoreshaping engagement with a flexible tubing;

FIG. 11 is a end view of the pumping element and reshaping fingers ofFIG. 10 shown in another sequential pumping position;

FIG. 12 is an end view of the pumping plate and reshaping fingers ofFIGS. 10 and 11 shown in yet another pumping position; and,

FIG. 13 is a end view of the pumping element plates of FIGS. 10, 11, and12 shown in yet another sequential pumping position according to thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts a schematic perspective view of an example of onepreferred embodiment of a linear peristaltic pump control box 10, havinga control panel 11 with control buttons 12, control display 13 and 14and indicator lights 15. The nature and arrangement of the control paneldisplay buttons and indicators can be as shown in FIG. 1 or in otherconfigurations as may become desirable. The linear peristaltic pumpcontrol box is constructed to releasably engage a flexible tubing 16along an engagement pathway 18, which is conveniently located along oneexterior surface 19 of the linear peristaltic pump control box 10. Also,schematically depicted is one preferred embodiment of a pumping elementand reshaping finger assembly 20, attached to control box 10 andpositioned along the engagement pathway 18 in exterior surface 19 of thecontrol box 10. The pumping element and reshaping arm assembly 20 mayadvantageously include a housing 22, which housing 22 is preferablyconstructed for attachment within the pump control box 10 or may beintegrally formed as part of the control box 10. The housing typicallytakes the shape of a box having sidewalls, ends and a bottom, as will bediscussed more fully below.

In the preferred embodiment depicted in FIGS. 1 and 2, the pumpingelement and reshaping finger assembly 20 includes a plurality of pumpingelements 24 and a plurality of reshaping fingers 26 which areinterdigitated between each of the plurality of pumping elements 24. Thepumping elements 24 and the interdigitated reshaping fingers 26 arepreferably constructed as flat, pumping plates 24 and flat reshapingfingers 26, respectively. In the embodiment shown, each of the pluralityof the pumping element plates 24 has an upper element cutout 30, whichallows the flexible tubing 16 to fit thereinto. The cutouts 30 of thepumping elements are aligned to define an engagement channel 28 alignedwith engagement pathway 18. Also, the plurality of interdigitatedreshaping fingers 26 include pairs of opposed fingers 26i and 26ii,which are aligned in planes between each of the pumping element plates24. The pairs of opposed interdigitated reshaping fingers 26i and 26iieach have corresponding opposed jaws 32i and 32ii. Each pair of opposedjaws preferably defines a substantially cylindrical opening having adiameter corresponding to the diameter of the flexible tubing 16.

In the preferred embodiment, there is a plurality of pairs of fingersalong the engagement length of tubing, and in a particularly preferredembodiment, the number of pairs of fingers corresponds to the number ofpumping elements, plus one. The pairs of jaws of the plurality ofreshaping finger pairs are pivotably attached so that a plurality ofcylindrical shaped openings are defined by the fully actuated jaws whichare coaxially aligned with the plurality of pumping element cutouts 30so that engagement channel 28 results. In the embodiment depicted, thereis a backing support bar 34, having a plurality of backing blocks 36projecting therefrom, with a plurality of gaps 38 between the backingblocks. The backing support bar 34 is attached to provide resistivesurfaces against which each pumping element can compress the flexibletubing 16. In the embodiment shown, engagement of the flexible tubing16, once inserted in channel 28, is accomplished using a backing supportbar 34 which pivots from an open or receiving position to a closedresistive support position. Support bar 34 in this embodiment isattached to pivot arms 44, which are pivotably engaged with pivot bosses42 so that the plurality of backing blocks 36 are attached along supportbar 34 so that all of the backing blocks 36 can be pivoted into anadjacent resistive support relationship to each of the pumping elementplates 24. The backing blocks 36, according to this embodiment, are thusaligned for partial insertion into the cutouts 30 of the pumping elementplates 24. Engagement edges 46 on the engagement bosses 40 can be movedunder a locking ledge 48 on a movable locking handle 50 which therebyholds the support bar 34 and backing blocks 36 in position. Theplurality of backing blocks 36 securely hold the flexible tubing 16within the engagement channel 28. The pumping element plates 24 can thenbe sequentially actuated to compress the flexible tubing against theplurality of backing blocks 36 in a sequential fashion. The gaps 38allow the reshaping fingers to contact the flexible tubing around an arcwithout interference from the backing blocks 36 or the support bar 34.With consistent size tubing, the backing blocks can be held rigidly inplace. In the preferred embodiment depicted, a small amount offlexibility is provided on the pumping element side to accommodate smallvariations of tubing size and/or tubing thickness. It will be understoodbased upon the disclosure herein that flexibility might also be providedas with a spring-loaded support bar or spring-loaded backing blocks (notshown).

Upon reading this disclosure, others may understand that other forms ofengagement pathways 18 may be formed without cutouts 30 in the pumpingelements. The backing blocks may be rigid or spring-loaded, for example.However, advantageously in such embodiments, gaps or spaces between thebacking blocks will facilitate movement of interdigitated reshapingfingers against the tubing, particularly where the fingers have concavejaws.

FIG. 2 is a schematic perspective view with a partial cutaway section ofthe inventive pumping plate and reshaping finger assembly 20. Thelocking handle 50 is attached to a pair of latch arms 52, whichcoaxially pivot about latch pivot axis 54. The latch pivot 54 mayconveniently be formed using a rod, a screw, a bolt or other fastenerwhich is attached to the housing. Another fastener rod 56 extendsthrough the plurality of reshaping fingers 26i along one side of thehousing. This provides a pivot axis for each of the reshaping fingers26i on one side of the assembly 20. Either latch pivot 54 or anotherpivot rod 56ii along the other side of the mechanism assembly 20, aswith fastener rod 56, may also be a rod, screw, bolt or other similarfastener which extends through reshaping fingers 26ii toward the opposedside of the assembly 20 to provide a pivot axis for the opposed fingers26ii of the pairs of interdigitated reshaping fingers 26.

Each of the plurality of pumping element plates 24 is preferably formedwith a cam follower opening 58, and each is driven with correspondingpumping element drive cams 60. Upon reading this disclosure, others maybecome aware of other mechanisms and ways to get cam actuation motion,according to this disclosure. However, in the preferred embodimentshown, each of the drive cams 60 is advantageously a rotary cam 60, andeach is secured to a drive shaft 62 so that a rotary camshaft resultswith a plurality of offset cam lobes. Each drive cam has a maximumeccentricity to drive each pumping element plate an equal distance aseach other (i.e., with the same stroke). Thus, each pumping elementreciprocates the same distance as each other pumping element.Preferably, all of the cams 60 are mounted to a single drive shaft 62,and all have the same amount of eccentricity; however, the maximumeccentricity of each cam is angularly offset from each adjacent cam apredetermined amount.

The drive shaft 62 extends through housing 22 for rotation as at bearing64. The drive shaft may be driven in rotation by a motor 70, which ispreferably a variable-speed motor. The driving force to the drive shaft62 may be provided directly from a motor or may be provided throughappropriate transmission mechanisms. In the embodiment depicted, a firstpulley or gear 68 on drive shaft 62 and a second pulley or sprocket 72on motor 70 are interconnected as with belt or chain 74. Preferably, thebelt or chain 74 and the pulleys or sprocket 70 and 72 are of a typewhich prevents slippage, such as a chain or a belt and pulley of thetype having mating teeth. The variable-speed motor is controlled by asignal 78 responsive to input from control panel 11 as may be input withcontrol buttons 12, which signal is provided to select the speed ofmotor 70 as through electrical connectors 76. This effectively controlsthe pumping rate of mechanism 20.

Advantageously, at least one pumping element of the sequence will be ina fully compressed position at all times, so that reverse flow isprevented. In a preferred embodiment, the angular amount of offset, toensure that at least one pumping element is closing the tubing, can becalculated by dividing 360° by the number of pumping elements, minusone, as in the following equation: ##EQU1##

This amount of angular offset between each cam in a sequence of anypredetermined number of pumping elements will ensure that at least onepumping element is in the fully compressed position at any given pointin the cam drive shaft rotation. If, for example, the first pumpingelement 24a, of a series of eight pumping elements 24a, 24b, 24c, 24d,24e, 24f, 24g and 24h, is in a fully compressed position (i.e., with thetubing in a fully closed condition), then the last pumping element plate24h of the series will also be in a fully compressed position when theangular spacing is calculated by the above formula, as follows: ##EQU2##At any other cam rotation position, one of the other pumping elementswill be fully compressed. In the embodiment depicted, there are eightpumping cams, and each cam is offset angularly around shaft 62 byapproximately 51.4° from each next adjacent cam 60a to 60b, 60b to 60c,etc., so that the first and the eighth cams 60h have their maximumeccentricity in the same angular direction with respect to shaft 62. Thefirst cam 60a actuates the pumping element 24a to a fully compressedposition, and the eighth cam 60h simultaneously actuates plate 24h to acompressed position and then it moves toward a released or openedposition. Each cam, in sequence, actuates a corresponding pumpingelement so that a column of fluid within the IV tubing 16 is moved fromthe first pumping element plate 24a, to the next adjacent pumping plate24b and in sequence along the engaged portion of the IV tubing and outpast the eighth pumping element plate 24h.

FIG. 3 shows a top plan view of pumping elements 24a, 24b, 24c, 24d,24e, 24f and 24h and interdigitated reshaping fingers 26a through 26h.FIG. 5 shows a schematic cross-section taken in a side direction along acenter line or a plane cut through the center of the pumping mechanism20 with reshaping fingers, as shown in FIG. 3, along section line 5--5.In FIG. 5, it can be seen that the plurality of cams 60a through 60heach have an equal maximum eccentricity, which is shown in FIG. 5, withfirst cam 60a and last cam 60h both being offset in a maximum downwardposition in substantially equal amounts. The centrally located cam 60dis offset with its maximum eccentricity upward, completely compressingthe IV tubing 16 against backing support bar 34, and in particular,against corresponding backing block 36d. As drive shaft 62 is rotated,each cam will be rotated against a corresponding pumping plate so thatits maximum eccentricity completely closes the tubing 16. As therotation continues, a wave-like action will pump fluid through IV tubing16, as depicted with the flow direction arrow 84.

Also, as depicted in FIG. 3, when compression plate 24d is fullyactuated to compress IV tubing 16, then IV tubing 16 will be flattenedin a vertical direction so that it spreads outward in a horizontaldirection. The cutout opening 30d is sufficiently wide to accommodatethe horizontal spreading. It will also be seen that as compressionplates 24a and 24h are both retracted downward in a vertical direction,IV tubing 16 tends to resiliently return to its original horizontaldimension. In order to facilitate the return of the tubing to itsoriginal shape, reshaping fingers 26a (which is correspondingly adjacentto pumping plate 24a) and reshaping fingers 26h (which iscorrespondingly adjacent to pumping plate 24h) are actuated inward asthe pumping plate elements 24a and 24h retract.

In the preferred embodiment, as shown in FIG. 2, there is at least onepair of reshaping fingers adjacent to each pumping plate. Mostpreferably, each end pumping element has two pairs of reshaping fingers,as shown in FIG. 4. In the embodiment of FIG. 4, additional reshapingfingers 26j are actuated simultaneously with fingers 26h by pumpingelement 24h. In this embodiment, the tubing on either side of eachpumping element is reshaped. Each finger has a jaw 32 such that a pairof jaws 32i and 32ii are positioned in an opposed relationship. Jaws 32iand 32ii are automatically moved inward against the exterior walls of IVtubing 16. Jaws 32i and 32ii act in opposite for directions for opposedreshaping contact. Thus, the IV tubing 16 which had previously beencompletely compressed (as shown at pumping plate 24d) becomes fullyreshaped by adjacent reshaping pairs of reshaping jaws 32i and 32ii whenthe pumping plate 24 is actuated in a retracted or non-compressiondirection.

With reference to FIGS. 6, 7, 8 and 9, which depict a sequential seriesof pumping plate actuations and corresponding reshaping fingeractuations. The pumping element compressions and releases, as well asthe corresponding action of the reshaping fingers are depicted at foursteps throughout an entire 360° rotation of cam drive shaft 62 for asingle pumping element plate 24a and a corresponding pair of reshapingfingers 26ai and 26aii.

With reference first to FIG. 6, the peristaltic pumping and reshapingmechanism 20 is shown encased within housing 22, which includessidewalls 90 and 92. Pumping plate 24 is actuated in compression andrelease (or up and down, as shown in FIGS. 6-9). Edges 23 and 25 of eachpumping plate 24 slide against the interior of walls 90 and 92,respectively. The lower portion of pumping plate 24 is guided in thepreferred embodiment with a guide boss 86 which projects from a bottom93 of housing 22, and which boss 86 is aligned with a groove 87 formedin pumping plate 24. Drive shaft 62 rotates the cams 60 (which rotationis schematically depicted with an arrow at a position indicated by a dot88). Each cam 60 is positioned between a spring-loaded projection 96 anda cam following surface 94 of pumping plate 24, so that the pumpingplate is reciprocated by the rotating eccentricity of cam 60. Pumpingplates 24 are preferably constructed of a hard plastic material, such asnylon, and projections 96 are preferably formed integrally with thepumping plates 24. The resiliency of the nylon material causes eachprojection 96 to act as a spring-loaded cantilever. This preferredarrangement advantageously provides a direct drive between the cam 60and the follower surface 94 when moving in a retracted pumping elementdirection. This is shown as a downward direction in FIGS. 6-9.Advantageously, when the cam 60 actuates the pumping plate 24 in adirection causing compression of tubing 16 against the backing block 36,there is a small amount of spring action available in projection 96 toprevent damage to the mechanism in the event of blockage. This springaction can accommodate manufacturing tolerances in the pump, as well assmall differences in total tube wall thickness from one manufacturer tothe next or in different manufacturing runs by the same tubingmanufacturer.

In the preferred embodiment, the materials for manufacturing the pumpingplates and the reshaping fingers are chosen for strength for lack offriction against each other and for chemical resistance. Advantageously,Delrin has been used for fingers, and nylon has been used for pumpingelements. Other considerations of manufacturing may dictate theparticulars of whether the fingers are Delrin and the pumping plates arenylon, or vice versa (i.e., nylon fingers and Delrin pumping plates).The object of reducing friction between the adjacent moving elementsmight also be accomplished by utilizing other materials according tothis aspect of the disclosed invention.

Turning to FIG. 7, the cam 60 is shown to be moved to a positionapproximately 90° from the position depicted in FIG. 6. This isschematically indicated by the direction arrow and position indicatordot 88 move to the position, as shown in FIG. 7. Also, it can be seenthat pumping element 24 is now moved upward with respect to the housing22, as schematically indicated with vertical movement arrow 98. It willalso be noted that in this position, tubing 16 becomes partiallycompressed because of the partial upward actuation and movement ofpumping plate 24. Also, finger driving cam surfaces 80i and 80ii, whichare formed in this embodiment as actuator channels 80i and 80ii, aremoved with pumping plate 24 in an upward direction with respect toreshaping fingers 26i and 26ii. Cam followers 82i and 82ii are fastenedto the fingers 26i and 26ii, respectively. Actuator channels 80i and80ii are formed at an angle such that vertical movement between theactuator channels 80i and 80ii and the followers 82i and 82ii results ina horizontal component of movement to cam followers 82i and 82ii. Thecam followers 82i and 82ii may be projections integrally formed on thereshaping fingers, or they may be pins projecting through the reshapingfingers. The reshaping fingers 26i and 26ii are pivotably mounted ataxes 54 and 56, respectively, which provide pivot points located abovethe actuator channels 80 and follower 82. Thus, reshaping fingers 26iand 26ii pivot in opposite direction about pivot points 54 and 56,respectively, causing jaws 32i and 32ii on fingers 26i and 26ii to moveoutwardly, thereby accommodating the additional horizontal width oftubing 16 due to its partial compression by pumping plate 24.

Referring now to FIG. 8, which is a depiction of the pumping andreshaping mechanism assembly 20 with shaft 62 and cam 60, shown rotatedanother 90°, as indicated with the arrow and position dot 88. Rotationof cam 60 will cause an additional amount of upward movement of elementplate 24, as indicated with vertical movement arrow 100. As actuatorchannels 80i and 80ii are moved upward, cam followers 82i and 82ii willbe pivoted inward about pivot rods 54 and 56 so that reshaping jaws 32iand 32ii at the top will be moved outward and will provide ampleclearance for complete compression of IV tubing 16 to a closed andcompletely flattened condition.

In FIG. 9, the peristaltic pumping mechanism 20 is shown with camshaft62 having rotated cam 60 an additional 90°, as indicated by directionarrow and position dot 88. This will move pumping plate 24 downward, asindicated by motion arrow 102, so that tubing 16 again becomes partiallyopened. The relative motion between actuator channels 80i and 80ii andcam followers 82i and 82ii will act to pivot the reshaping fingers 26iand 26ii outward at the bottom and inward at the top, so that thereshaping jaws 32i and 32ii contact the previously compressed IV tubing16 in opposed horizontal directions, thereby returning tubing 16 towardits original shape and an opened condition. Where the reshaping jaws 32iand 32ii are in the shape of concave arcs of a cylinder, with the sameradius as the tubing 16, the tubing 16 will be reshaped to its originalcircular cross-sectional shape.

Reference again to FIG. 6 shows cam 60. The rotation direction arrow andposition dot 88 indicate that cam 60 has been moved another 90°, therebycompleting 360° of rotation, which moves pumping plate 24 to a fullretracted position. This fully releases vertical compression from tubing16. The relative motion between actuator channels 80i and 80ii withrespect to followers 82i and 82ii acts to pivot reshaping fingers 26iand 26ii so that jaws 32i and 32ii fully engaged in opposed horizontaldirections, thereby reshaping tubing 16 to its full circularcross-sectional condition.

Thus, it can be seen that due to the configuration and construction ofthe depicted embodiment of the invention, in which a plurality ofreshaping finger pairs are interdigitated with the plurality ofperistaltic pumping plates, the reshaping jaws 32i and 32ii can each beadvantageously formed in the shape of an arcuate, concave surface whichreshapes the tubing 16 to a substantially circular cross-section,thereby consistently returning it to its full volume at the point ofreshaping jaw contact. Each jaw preferably contacts tubing 16 with anarc which is greater than about 90° so that more than about 180° of acircular shape results at total actuation of both reshaping jaws 32against tubing 16. The reshaping contact occurs sequentially andalternately with the compression of the tubing. Throughout the operationof the peristaltic pumping mechanism 20, the tubing 16 is reshaped sothat the interior volume of tubing 16, and thus the volumetric pumpingrate for any given rotation speed of cam drive shaft 62, remainssubstantially constant throughout the operation of the peristalticpumping and reshaping mechanism 20. Also, advantageously reshaping ofthe tubing 16 to its previous natural circular cross-sectional shape,without introducing new bends, reduces the introduction of new stressesand therefore reduces the fatigue to which tubing 16 is subjected,compared with reshaping as might be attempted without concave jaws. Theuseful life of a given portion of IV tubing is advantageously extended.In the case of a tubing 16, for example, this not only reduces costlymonitoring and time-consuming replacement, but also it reduces potentialfor trauma to a patient due to or during IV replacement. Moreover,reshaping to a rounded shape facilitates accuracy by maintainingsubstantially the same return shape volume as with new tubing. Theunique and unobvious interdigitated relationship between pumping plates24 and reshaping fingers 26 advantageously allows the reshaping fingers26 to be formed, having a concave, arcuate jaw shape, withoutinterfering with the pumping elements themselves. Each jaw may be nearlysemicircular so that complete reshaping is facilitated.

Turning now to FIGS. 10 through 13, an alternate embodiment of theinvention is depicted, in which an alternative peristaltic pumping andreshaping mechanism 120 includes a housing 122 and sidewalls 190 and192. There is a plurality of pumping plates 124 positioned therein alongwith a plurality of pairs of reshaping fingers 126. Each finger 126i and126ii of the pair 126 has a corresponding reshaping jaws 132i and 132ii,respectively. The pumping element 124 is shown in the form of a pumpingplate 124, which has angled finger driving cam surfaces 180i and 180iiformed thereon. Cam followers 182i and 182ii are attached to or formedon reshaping fingers 126i and 126ii and are slidingly held against thecam surfaces 180i and 180ii, respectively. The reshaping fingers 126 ofthis alternative embodiment are preferably constructed of a resilientplastic material, such as nylon, and are preferably formed to have arms104i and 104ii, which are biased outward against sidewalls 190 and 192.The material of which the reshaping fingers 126i and 126ii areconstructed is preferably resilient so that arms 104i and 104ii can beintegrally formed with the reshaping fingers using cutout areas 106i and106ii. This construction results in a spring-like action, whenconstructed of resilient material or which could be supplied byinserting a spring, such as a metallic coiled spring. This isschematically represented by depictions of springs at 108i and 108ii.Thus, cantilever projections or arms 104i and 104ii are "spring-loaded"against the inside walls 190 and 192. The spring tension, schematicallydepicted as 108i and 108ii, keeps the cam followers 182i and 182ii inconstant contact with the respective finger driving cam surfaces 180iand 180ii of pumping element place 124.

FIG. 11 depicts the peristaltic pump and reshaping assembly 120 of FIG.10 in a position at which cam 160 is rotated 90° from the position shownin FIG. 10. In this position, tubing 16 is partially compressed, and camfollowers 182i and 182ii are moved inwardly along angled cam surfaces180i and 180ii due to the upward motion of pumping plate 124. The cutoutopenings 106i and 106ii are shown expanded slightly due to theresiliency of the material from which the reshaping fingers 126i and126ii and arms 104i and 104ii are constructed, thereby providing thespring tension which is schematically depicted as 108i and 108ii. Themotion of the cam followers inward at the bottom results in outwardmotion of concave reshaping jaws 132i and 132ii at the top. Theoperation is similar to that in the alternative embodiment previouslydepicted in FIGS. 6-9, except that the pumping plate 124 and thereshaping fingers 126i and 126ii are constructed differently,particularly in the area of the angled finger driving cam surfaces 180iand 180ii and the corresponding cam followers 182i and 182ii which arenow provided with "spring loading" to maintain cam and follower contact.

Referring to FIG. 12, the maximum upward motion of pumping element 124is achieved with the cam 160 having its maximum eccentricity rotated toan upward position. Cam followers 182i and 182ii move along angled camsurfaces 180i and 180ii to their maximum inward position, thereby movingjaws 132i and 132ii to their maximum outward position so that anyhorizontal expansion of tubing 16 due to its compression to a completedclosed condition is accommodated.

FIG. 13 depicts pumping element plate 124, partially retracted. The camfollowers 182i and 182ii move along the cam surfaces 180i and 180ii,thereby causing the reshaping jaws 132i and 132ii to move inwardly,partially reshaping tubing 16. As with the embodiment depicted in FIGS.6-10, reshaping is accomplished automatically as pumping plate 124 iswithdrawn. The cycle is completed as shown in FIG. 10 in which tubing 16is completely reshaped to its round, cross-sectional shape when thereshaping jaws 132i and 132ii move to their maximum inward position. Thecorresponding opposed jaws 132i and 132ii preferably define asubstantially circular cross-section or cylindrical shape therebetweenwhen pivoted fully inward. Reshaping of the flexible tubing 16 iscompleted immediately adjacent to each pumping contact point.

Other alterations and modifications and equivalents of the invention andits elements will likewise become apparent to those of ordinary skill inthe art upon reading the present disclosure, and it is intended that thescope of the invention disclosed herein be limited only by the broadestinterpretation of the appended claims to which the inventors are legallyentitled.

What is claimed is:
 1. A linear peristaltic pump for moving fluidthrough a flexible tube comprising:(a) a housing; (b) a tube receivingchannel; (c) a closable door pivot by attached to said housing to holdsaid tubing into said tube receiving channel; (d) a plurality of pumpingplates each slidably held in said housing for contacting said flexibletube and each pumping plate positioned at a spaced apart interval fromanother pumping plate, for contacting said tubing; (e) a plurality ofcams on a rotary shaft engraved with said pumping plates forsequentially reciprocating said pumping plates to compress and releasesaid flexible tube so that fluid is moved therethrough; (f) a pluralityof pairs of opposed reshaping fingers pivotably mounted in said housing,each pair of opposed reshaping fingers position in said spaced apartintervals between said pumping plates; (g) actuator channels formed onsaid pumping plates for engaging said pairs of reshaping fingers and forsequentially moving said pairs out of and into reshaping contact withsaid flexible tube upon reciprocation of said pumping plates to compressand release said flexible tube, respectively.
 2. A linear peristalticpump for moving fluid through a flexible tube comprising:(a) a housinghaving a tube receiving channel; (b) a door having a backing surface,said door connected to said housing to be releasably engagable so thatsaid backing surface is adjacent to said tube receiving channel; (c) aplurality of pumping plates, each having a tube contacting surface andeach one of said pumping plates movably mounted in said housing adjacentto another one of said pumping plates forming a plurality of spacesthere between; (d) a plurality of cams mounted on a single rotary driveshaft for sequentially moving said pumping plates into and out of saidtube receiving channel; (e) a plurality of pairs of opposed reshapingfingers pivotably mounted interposted in said plurality of spaces formedbetween said pumping plates; (f) cam surfaces formed on each of saidpumping plates slidingly engaged with said interposed pairs of reshapingfingers for pivoting said opposed reshaping fingers out of and partiallyinto said tube receiving channels upon reciprocation of said pumpingplates into and out of said tube receiving channel.